Treatment of wood with aminofunctional silanes for protection against wood destroying fungi

Abstract

Different aminofunctional silanes were tested for their suitability to preserve wood against basidiomycetes in a mini-block experiment according to EN 113. High effectiveness against the brown rot fungusConiophora puteanawas maintained over prolonged exposure times of up to 18 weeks. Resistance against the white rot fungusTrametes versicolorwas only enhanced in the initial phase of exposure (6 weeks); after longer exposure times of 18 weeks, considerable mass losses were observed. It was shown that the antifungal resistance was caused by the amino groups of the oligomeric silane systems, while alkyl groups, which influence the water uptake of wood, only had a minor impact. For effective protection, acidic conditions of the treatment solution were important; this promotes the formation of cationised amino groups (ammonium). The silane quaternary ammonium compound (Si-QAC) 3-(trimethoxysilyl)propyldimethyloctadecyl ammonium chloride was applied in combination with an oligomeric silane system to incorporate quaternary ammonium sites into a SiO2matrix via a sol-gel process. This combined treatment significantly enhanced the decay resistance of pine wood againstC. puteana.

Potential contribution of organosilicon compounds to reduced leaching of biocides in wood protection

“…Isquith et al (1972) demonstrated that the Si-Quat had antimicrobial activity in a serial tube dilution method without entering the cell and attributed this activity to membrane phenomena. Donath et al (2006b) proved the Si-Quat to be also effective in protecting Scots pine sapwood against fungal decay by C. puteana when incorporated in a siloxane matrix. The Si-Quat was applied at a concentration of at least 0.5% ai in combination with 5% ai multifunctional silane.…”

“…It is not surprising that the leachates are toxic and it is clear that lower concentrations of IPBC would still be effective against decay and yield lower toxicity towards D. magna. Donath et al (2006b) have treated Scots pine and beech mini-blocks with a multifunctional silane alone or in 209p5 combination with 3-(trimethoxysilyl)propyldimethyloctadecyl ammonium chloride (Si-Quat). After EN 84 leaching the recorded mass losses were about the same irrespective the addition of the Si-Quat to the treating solutions.…”

“…Furthermore, once the retention of the biocides in the wood falls below a certain threshold, the retained biocides are no longer able to protect the wood adequately. It has been suggested that water repel-* Corresponding author: liesbeth.devetter@ugent.be lents like oils, waxes and silicones, can be combined with biocides for wood in use class 3 conditions being outdoor usage out of ground contact (Donath et al, 2006a;2006b). The primary purpose of these products is to interfere in the woodmoisture relation to protect the wood, but they are also supposed to prevent leaching of biocides during service life (Donath et al, 2006a;2006b;Mai and Militz, 2004;Taylor and Cooper, 2003;Zahora, 2000).…”

“…It has been suggested that water repel-* Corresponding author: liesbeth.devetter@ugent.be lents like oils, waxes and silicones, can be combined with biocides for wood in use class 3 conditions being outdoor usage out of ground contact (Donath et al, 2006a;2006b). The primary purpose of these products is to interfere in the woodmoisture relation to protect the wood, but they are also supposed to prevent leaching of biocides during service life (Donath et al, 2006a;2006b;Mai and Militz, 2004;Taylor and Cooper, 2003;Zahora, 2000). Their suitability, mode of action and location inside wood once applied has been investigated (De Vetter et Article published by EDP Sciences positive results, also conflicting data are reported about the effect of water repellents, e.g.…”

“…Drawbacks are its known toxicity towards fish and daphnids (Cook et al, 2002). Testing quaternary ammonium compounds showed their effectiveness as wood protecting agents, but they may leach out and pose a threat to both mammals and humans (Donath et al, 2006b). The triazole fungistatic compound propiconazole prevents or blocks fungal growth by binding to the enzyme sterol 14α-demethylase, thereby preventing synthesis of ergosterol, an essential part of fungal cell walls (Zarn et al, 2003).…”